The average feature-set of mobile phones available in the market has steadily increased over last years, driven by both technological advances and market demand. As a result of this trend, nowadays, the most capable mobile devices, sometimes referred to as smartphones, are capable of executing a large number of tasks, in addition to classic telephony services. Such features include, for instance, accessing the Internet, running relatively computation-intensive applications, playing or recording a plurality of media contents and store large amounts of data. Subsequently, the larger set of functionalities being provided by mobile devices has led to a change in mobile phones usage by end users.
One of these changes is represented by contents that users are storing on their devices. In fact, end users are now capable of storing locally on mobile phones an increasing amount of data, some of which can be very sensitive. Examples include emails, documents, photos, videos, passwords and other authentication credentials. Even in cloud computing contexts, where large part of the computation and storage is executed by server-side applications, mobile devices still store a considerable amount of sensitive information, such as authentication credentials and data which are locally cached for performance and availability reasons.
Since devices can be very easily subject to theft or loss, the security of data and, more generally, of any other local resource of a mobile device, such as applications or hardware components, is a considerably important matter. For this reason, the increasing amount of locally available resources on mobile devices is resulting in tighter security requirements to appropriately protect them.
Currently, in 3GPP-compliant mobile phones, security can be provided by the utilisation of a Subscriber Identification Module (SIM) or a Universal Subscriber Identification Module (USIM) installed on a tamper-resistant integrated circuit card, sometimes referred to as Smart Card. A (U)SIM can be used to mutually authenticate a mobile subscriber and a mobile network and to provide confidentiality, integrity, authenticity and non-repudiation to the data exchanged between a mobile phone and a 3GPP-compliant mobile network.
(U)SIMs provide an appropriate level of security for accessing mobile network services. In fact, differently from username/password authentication credentials, which provide “something-you-know” one-factor authentication, (U)SIM applications on smart cards provide a stronger “something-you-have” authentication. Furthermore, (U)SIM security can be increased through the setting of a Personal Identification Number (PIN) to protect access to the card to unauthorised users, thus enabling the (U)SIM to provide two-factor authentication. In conclusion, another noteworthy security feature of a (U)SIM consists in the capability to be deactivated remotely by a mobile network operator.
However, the use of authentication mechanisms based on (U)SIM as means for securing local resources on a mobile device presents considerable limitations.
First, (U)SIM-based authentication cannot be executed if no network connection is available. In fact, both GSM and UMTS Authentication and Key Agreement (AKA) protocols require the availability of a mobile network to generate an authentication challenge and to validate the response provided by the (U)SIM.
Second, an attacker can run an AKA authentication between a spoofed (U)SIM and a spoofed mobile network to induce the device into believing that the (U)SIM is genuine and therefore authorizing access to local resources.
Third, (U)SIM-based authentication protocols do not provide appropriate mechanisms to encrypt/decrypt locally stored files and to verify their integrity.
Nevertheless, a person skilled in the art would recognise that these capabilities could potentially be provided by a specific additional applet installed on a SIM card or a Universal Integrated Circuit Card (UICC). However, this would require specific cards to be issued, which would represent a serious limitation for a large scale deployment. In fact, it would require the replacement of the cards currently deployed or to install the applet over the air and both procedures would be considerably expensive. In addition, in case also online security features are required, such as remote deactivation and online authentication when network connectivity is available, a dedicated network infrastructure would be required, with a further increase in both capital and operational costs.
WO-2007/036024 discloses a method for providing authentication of a user of a recipient unit when the recipient unit is offline. The method includes storing one or a plurality of challenge-reply sets associated with an article based on an online communication with a sender unit. Each of the challenge-reply sets includes at least a challenge-reply pair for use in offline authentication of the user for a particular resource available through the recipient unit.
However, the method disclosed in this document does not recite the adaptation to an identity module environment. In other words, this method does not permit the authentication within the framework of a separate module.
Embodiments of the present invention will improve the situation.